Stabilized caprolactam polymer composition



United States Patent 3,113,120 STABILIZED CAPROLACTAM POLYMER COMPOSITION Patrick V. Pspero, Jr., Chester, and Robert L. Morter, .lr.,

Hopewell, Va assignors to Allied Chemical Corporation, New York, N.Y., a corporation of New York No Drawing. Filed June 14, 1960, Ser. No. 36,089 10 Claims. (Cl. 260-42) This invention relates to a polycaproamide compo sition which is resistant to the deteriorating effects of light, outdoor weathering. and heat.

It has been proposed to improve the aging resistance of polyamide compositions and articles by incorporating copper in the form of copper compounds which dissolve in molten polyamide whereby poiyamide having copper dissolved therein and/or reacted therewith is obtained. The resulting polyamide has definitely improved aging properties as compared to the polyamide similarly produced but without copper, but there is still room for further improvement in the aging properties and there is a distinct disadvantage in that the copper present produces coloration in the polyamide product.

We have now found that when an arylsulfonic acid free of chromophoric groups, or salt thereof, especially p-toluenesulfonic acid, is included in polycaproamide compositions having copper dissolved therein, in molecular proportions of sulfonic acid:atomie proportions of copper of at least about 3:l, preferably about 10: 1-500: 1, the resistance of the resulting polycaproamide composition to outdoor weathering is considerably enhanced. Moreover the composition shows very good stability to light and to heat, and the color of these polycaproamide compositions is white or nearly white even though the polymer has copper dissolved therein.

We have found that our above described stabilized polycaproamide compositions are, moreover, amenable to still further improvement of their thermal stability by addition thereto of an aryl organic nitrogen or phosphorus containing antioxidant, particularly an antioxidant based upon a diarylamine. Our preferred type of organic antioxidant ingredient is a diarylamlne-kelone reaction product which is characterized by its containing the mesa dialltyl acridan nucleus. Especially effective, we have found, is the high temperature, high pressure diphenylamine-acetone reaction product further reacted with formaldehyde to form a water-insoluble, solid fusible condensation product. The antioxidant can be included in amounts suitably between about 0.1% and about 25% by weight based on the weight of polycaproamide. Polymer containing as much as 10-25% of its weight of antioxidant will generally be used as a master batch, to introduce the stabilizer system into unslabilized polymer; the usual level of antioxidant in the polymer intended for end uses will ordinarily not exceed about 5% by weight based on the polymer weight.

Preferably our compositions have copper compound dissolved therein in proportions providing a content of dissolved copper between about 5 and about 500 ppm. by weight. Especially preferred proportions of copper compound In view of the good stability and low color obtained therewith in our compositions, are proportions providing copper content in the eaprolactam polymer 3,113,120 Patented Dec. 3, 1963 composition between about 10 ppm. and about 100 p.p.m. by weight. Proportions of the sulfonic acid preferably used are between about 0.1% and about 1% by weight of the caprolactam polymer composition. Larger amounts can be used but because the acid limits the molecular weight attainable in the polymerization of caprolactam in proportion to its concentration in the reaction mixture, the amounts used ordinarily will not exceed about 2% by weight.

It will be evident to those skilled in the art, from the fact that salts of sulfonic acids can be used instead of the acids in our compositions, that the acid function is not essential and that derivatives hydrolyzable to the acids such as esters, amides, etc. can be expected to function as equivalents of the acids.

A preferred copper compound is cupric chloride since polycaproamides having this compound dissolved therein together with specifically p-toluene-sulfonic acid incorporated therein, are particularly amenable to improvement in heat stability by addition thereto of an antioxidant based upon a diarylamine; have a good white color; and afford yarns which dye much more deeply than yarns from compositions based on certain other copper compounds.

The following examples describe completely specific embodiments illustrative of our improved compositions and methods of obtaining them; but it is to be understood that the invention is not limited to all details of the examples.

EXAMPLE I The following materials were charged to a stirred 1500 ml. Erlemeyer glass flask in the order given:

800 g. e-carpolaetam 8 g. distilled water 7.2 g. p-toluenesulfonic acid-i.e. 0.042 gram-molecule 0.08 g. cupric phosphate trihydrate (Cu,(PO.) .3H;O),

i.e. 0.00055 gram-atom of copper The reactants were heated to -90 C. and thoroughly mixed until a solution was formed; the solution was then charged to a 1500 ml. glass resin flask. The resin flask was equipped with a stainless steel type 316 anchor-type agitator and stuffing box, a vertical condenser so arranged that either water or steam may be admitted to the jacket, a thermocouple in a stainless steel well, an inlet for nitrogen and an electric heating mantle.

After the solution had been charged. the resin flask was purged free of air with dry nitrogen containing less than 5 ppm. oxygen. A blanket of this oxygen-free nitrogen was maintained under a back pressure of one inch of water in the vessel throughout all of the subsequent operations described below.

The reactants were polymerized using the following time-temperature cycle:

7 hours-90410 C.

5V: hours-2l0-255 C.

12 hours-255' C. (reaction) During the period of heating up and refluxing 210' C.), the resin flask was maintained at total reflux; cold water was used on the condenser and all distillate was returned to the reaction. When the temperature reached 210' C. (approximate boiling point of 99% lactam and 1% water), the reaction was maintained at this temperature for one hour. At the end of the period of refluxing the fiow of water to the condenser was shut oil and a flow of low pressure steam through the condenser jacket was maintained during the subsequent polymcrization operations. The use of superheated steam in the condenser facilitates the removal of water from the reaction mass during polymerization.

The mixture was next heated to 255 C. in hours. during which time water was continually removed (kettle on zero reflux). The distillate contained approximately 24% lactam. The contents of the resin flask began to thicken noticeably at 230-235 C. The reaction temperature of about 255 C. was maintained for 12 hours. During this period the polymeric chains continued to form and reached an equilibrium state because of the chain-terminating property of the sulionic acid employed, as indicated by levelling of the viscosity of the polymer product.

At the end of the heating period the agitator was stopped; the thermowell and agitator were pulled up and out of the melt; and the electric heating mantle jacket was turned ofi and removed from around the vessel, allowing the molten polymer to solidity. Air was prevented t'rom coming in contact with the molten mass by continuing the flow of nitrogen through the vessel until the polymer had cooled to about 50'-60' C.

After the polymer had solidified and cooled, the apparatus was dismantled and the bar of polymer was removed. The bar, approximately 4 inches in diameter and 6 inches long was cut into cubes (Vi inch x 36 inch x i6 inch) and ground in a Wiley mill to pass through a No. standard sieve (840 micron openings).

The ground polymer was then washed in a suitable agitated glass apparatus with distilled water at 100' C. (ratio polymer to water 1:1.2) for 2 hours; the water was removed and fresh, previously boiled distilled water (free from air) was added in the same ratio. A total of 5 washings was made and the polymer was then placed in a stainless steel tray for drying. During these operations a blanket of nitrogen was always used when polymer was exposed to the atmosphere.

The washed polymer was dried under a vacuum of inches of mercury at 85 C. until analysis indicated a content of water below 0.1% (about 48 hours).

The dried polymer was tested for formic acid relative viscosity by ASlM Method D-l89-5 3T.

The polymer was spun and drawn into a 10-filament yarn having weight approximately 60 denier after being drawn in a conventional manner.

The yarn, wound on aluminum bobbins 2 inches x 2 inches in dimension at 0.5 gram per denier tension, was exposed to accelerated weathering and light stability tests as follows:

A. Exposure in an Atlas weatherometer. Samples were exposed to carbon arc radiation of 3000-7000 A. wavelength. A distilled water spray was given 10 minutes each hour. The temperature of the unit was maintained at ll60 F.

B. Exposure to ultraviolet radiation of 2537 A. wavelength.-Samples were exposed in a geometric pattern to radiation from germicidal type fluorescent bulbs for 96 hours. The samples were constantly rotated for even exposure. The relative humidity was maintained at approximately 65%.

C. Exporurc to ultraviolet radiation 0] 4000 A. wavelength-Samples were exposed in a geometric pattern to radiation from a Sylvania RS sunlight bulb for days at room temperature. The samples were constantly rotated for even exposure. The relative humidity was maintained at approximately 65%.

D. Exposure to fluorescent light of 4000-7000 A. wavelcngrla4amples were exposed for 45 days as in test "C above to light from fluorescent bulbs principally in the visible region, 4000-7000 A.

Outdoor exposure tests were made as follows:

Yarn samples, rewouad at tension of 0.5 gram per denier on bobbins 2 inches x 6 inches in dimension, were placed on an outdoor rack inclined at 45 degrees facing due south. The samples were tested ever 30 days until they had lost more than of their original strength. Control samples were made by polymerizing by the procedure of this Example I except that no salt or acid was used, the polymerization being regulated by the water vapor pressure maintained in the reaction vessel atmosphere to afl'ord about the same formic acid relative viscosity in the comparison samples; the samples were spun and drawn as above. The control yarns were exposed simultaneously with the test yarns.

Table I represents results of such tests, illustrating the thermal and light stability of polycaproamlde yarns prepared from compositions of this invention. it also indicates the efleet of varying concentrations of p-toluenesulfonic acid on the light and weathering stability of the various polyamide compositions.

PERCENT IN ULTIMATE TENSILE STRENGTH Wit. Accelerated Weathering 1 Outdoor Exposuro 1 Wet. Percent No. Percent Copper P'IBA P os- W.0. UN. Floor. I0 00 I20 150 phato Days Days Days Days Days Yam 1 0.9 0 10 2t 0 ll ll 20 50 71 Control I 0 0 18 so 56 e2 83 Yam 2 0.0 .01 I! 7 It it t! 28 26 Control 2......... 0 0 10 23 ll (3 0B Yam 3 0. 0 .01 It 29 20 20 80 Control I 0 0 20 42 4t 01 M Yam 4.. 0. t .01 29 to so 48 (B Control 4 0 0 t? 68 It 74 some arn batons exposure.

0 oatharornotor exposure at t Ultraviolet exposure at (C a'olsht percent based on saprolactam. I l um llstnd sis percent losses in ultimate mantle Itronsth ot the tort sample compared to a sample ot the (Al above, 02 hours. above.

l Fluorescent exposure ot above.

5 Remarks on Table I:

(l) The weathering resistance of the yarns with the additives tested is clearly superior to that of the controls.

(2) Higher concentrations of p-toluenesulfonic acid, with a given concentration of copper phosphate, improve both light and weathering resistance of the yarns.

(3) Visual observation showed that higher concentrations of the p-toluenesulfonic acid, with a given concentration of copper phosphate, increase the whiteness of the resultant yarns.

EXAMPLE II A reactor, 227 liters in size, equipped with an anchor type agitator and horizontal water condenser, Dowtherm heated, and having only stainless steel types 304 and 3'16 in contact with the reactants and product, was charged with the following:

190 kg. e-caprolaetam 0.572 kg. ptoluenesulfonic acid-Le. 3.3 gram-molecules 21.2 kg. distilled water 0.0187 kg. cupric phosphate trihydratei.e. 0.13 gramatom of copper The charge was polymerized generally as in Example I under about 4 inches of water back pressure of nitrogen on the polymerization kettle. The following polymerization cycle was employed:

7 hours-450410 C.

1 hour-210' C. (reflux) 5'6 hours-210455 C.

14 hours-0.55 C. (on temperature) The polymeric material was extruded as a ribbon over a 3-hour period under pressure of moist inert gas saturated with water at 90-95' C. The ribbon was pelleted into chips 0.1 x 0.1 inch in size. The chips were then washed at I C. with distilled avater for 2 hours at a water to polymer ratio of 1.2:1; a total of washings was made. the polymer was then dried at 100 C. using a heated dry, oxygen-free nitrogen stream until the moisture content was reduced to less than 0.1%.

The chips were then melt spun, using extruder type melt spinning apparatus, into 32-filament yarn having an undrawn denier of approximately 1050. After drawing the yarn had a denier of 210.

The finished yarn was evaluated by the accelerated testing methods above described and by outdoor exposure as above described. The results obtained are shown opposite "Ex. II" in Table 11 below.

EXAMPLE III 5 Using essentially the procedure described in Example II the following charge was polymerized:

190 kg. ecaprolaetam 0.858 kg. p-toluenesulfonic ncid--i.e. 4.9 gram-molecules 1.925 lags-distilled water 10 0.0144 kg. cupric potassium chloride dihydrate (CuCl,.2KCl.2H:O)-i.e. 0.045 gram-atom of copper EXAMPLE IV a Using essentially the procedure described in Example 16 II, the following charge was polymerized:

from that of Example IV as in Example II and was evaluated as in Example 11. Additionally the thermal stability was determined as follows:

Samples of the test yarns were wound under constant tension of 0.5 gram per denier on 2 inch x 2 inch aluminum bobbins and then placed on a revolving rack (20 r.p.m.) in a forced draft oven maintained at 165:2 C.

After exposure the yarns were allowed to stand or a minimum period of 2 hours in an atmosphere controlled at 65% relative humidity. The yarns were tested before and after exposure by total destruction on a Scott IP-4 tensilgraph. Results are reported as percent loss in ultimate tensile strength (abbreviated as UTS) as compared to the ultimate tensile strength of the yarn before exposure.

The following Tables II and III (A and B) show the results of tests of the above-described yarns and of tests of other yarns (Exs. V-IX) produced by essentially the same procedures except as indicated in the tables. Also the tables show results of tests on yarns similarly produced but omitting salt and acid in the polymerization, designated Controls, tested in the same manner as the yarns of the examples. Tables II and III also show results with commercial aging-stabilized nylon 66 yarns tested for comparison in the same manner as the yarns of the examples.

Table II AOOELERA'IE'D LIGHT STABILITY AND OUTDOOR WEATIIEIIING [Determtned on above duerlbed hr Table I] Accelerated Testing Loss Outdoor Yarn E: are i aye) Yarn Percent Wgt. percent 01 Copper Salt Cu. W. 0. U. v. U. V. Floor.

PTBA p.p.m. 198, 2537 It. 4000 A. Om-M0 hrs. so hrs. 45, days A. Ubdnys Danlar Nlg ol (A) (a o r i so so so no Ex. II. 0.80 0.01 Om SI'Or) 1110"... 44 210 82 it so It 22 29 311 Nylontlt! stitchllw 210 I4 24 44 22 29 36 Es. 11L 0. 46 .023 OuO sJKOLQIIrO... 45 210 3'2 3t) 86 13 4t! 51 Nylon ea Btnhlltmd) 210 84 24 as 22 20 36 15!. IV t). 00 .012 OuO |.2lIs0.. 46 210 82 10 42 13 0 7 20 Nylon 00 Btahlllzae) 210 84 12 H 19 1B 15 21 El. V 0. 50 .17) OIIOLIKOLQIIIO. 40 840 I30 10 41 85 ll 83 86 Nylon M Stabllt 840 13 40 M 40 48 48 Ex. Vlt 0.50 .012 OuOsfllhO 45 M0 It 80 b Nylon 06 (Btabtllmi). M0 H0 18 to to I p-Toluomrultontc acid, welslitporoent based on eaprolnotam.

Table 111(A) THERMAL STABILITY [Determined as above described following Example IV] Relative Yarn Thermal Stability st Wgt. Per- Formie 105 C. Yarn cent Wgt. Percent of Copper Salt Cu. Acid Vis- PTSA l p.p.m. easily at Polymer I Denier No. at 30 100 Fiis Hours Iiuurs Hours 0.01 Cufli'Odsll'hCL. (4 59. 7 2l0 32 7 ll 21 0.023 CuCls.2KCl.2llsO 45 58. 4 2l0 32 5 0 22 0.012 CuCl:.2l.hO.- 45 67. 7 2l0 32 0 14 22 0 0 55. 7 200 i0 '71 (Stabilize 2l0 3i i0 23 0.012 CuClgJlhO 45 00. 9 840 130 7 0.02 CUCI:.2KCI.2II10-.- 40 47. 2 840 136 33 24 0.012 12 1:.2lIrO 45 53. 4 B40 130 l2 l4 (Stabilized) 40. 0 840 140 I7 22 20 I Pam-toluenesulionlo acid. weight percent hosed on coproiactnm. 1 AB'IM Method No. 0-780-63 Figures listed are percent loss in ultimate tensile strength alter the number oi hours exposure shown in the heading. Samples exposed for 24 hours only.

Table 111 (B) THERMAL STABILITY lDotermined as above described ioliowing Example IV] Relative Yarn Thermal Stability Formie at 15C. Yum W t 9,, 'gt. percent of additives Cu. Acid Vis- P 8A p.p.m costly of Polymer i Denier No. of it 100 I-ils iiours Iiours Hours 0.50 0.02 CuClrJKClJlhO plus 0.7 47.2 840 130 14 ll antioxidant. 0. 0.0il CuCh.2iI|0 plus 0.75 antl- (5 55. 6 840 I36 2 4 l6 oxidant. 0 0.10 Antioxidant. 0 b8. 7 840 130 0 0.20 Antioxidant. 0 b8. 7 840 X343 0 0.76 Antioxidant L. 0 b8. '1 B40 130 Para-wluenasuiionie acid, weight percent based on ceprolactam. A8'IM Method No. l.)-7B053T.

I Figures listed m t A rubber antioxidant, reaction dimathy aertdan nucleusI and tart r reacted vr (localised. in v.5. Patent 900.036 of May llama "LIXA." "l! A" banana ethylene dichloride; insoluble in water and gasoline.

chloride; iruo lublo In water and gun lno. The "l-laxamina" was formaldehyde to term a water-insoluble sol o ms to Horst, in particular in Exam is A and Exam a i thereoi. act of acetone and di hen lamina is suppl d by tho Naugatucl: Chemical Div tics: in ultimate tensile strength alter the number of hours exposure shown in the hcadin Fiaxamina,"-which is about 35% by weight N,N'-diphonyi-p-Alhan icnediamlne and as not oi acetone and di hcnylamine lormod at relatively high temperatures an n at United tsios Rubber 00. under the rude desaibod by the supplier as having a ellle gravity l.l0' melting range so i095 0. soluble in acetone Two antioxidant "F nmina" is also supplied is described by the supplier as havin apcciilo gravity 1.20; melting range 76' C. 1090' 0.:solublo incorporated in the polymer parts partial parts by we ht oi aqueous 90% lactarn) and polyrnarlzln at 266' 0. under atmospheric pressure generally as in by Neugatuelr. ii in acetone bennene, ethylene diby dissolving in eaproiactam lgilt hon pollctlng an blending to the specified concentrations wit polymer pellets produced essentially by the procedure oi that example above in which the stated copper salt was used.

Remarks on Table III:

(A) The outstanding thermal stability imparted to polycaproamidc yarns by use of the various copper sells in conjunction with p-tolucnesulfonic acid even up to 100 hours exposure at 165' C. is evidenced by the results obtained. compared to the controls containing no additivo and containing increasing amounts of antioxidant but no copper. The yarns obtained had a good white color.

(B) The addition of the cited antioxidant i'urther markedly improved the thermal stability of the yarns from the polycspmamidc/coppcr salt/p-tolucncsulfonic acid compositions-compare Ex. VIII vs. Ex. V1 and Ex. IX vs. Ex. VII. The yarns produced using this antioxidant wcre colored tan.

As shown in the above tables. the light and weathering stability of polycaproamide having various polyamidcsoluble copper salts and p-tolucncsulfonlc acid incorporated therein is excellent. The most effective copper salts impart stability to light and weathering equalling and exceeding that of the commercial aging-stabilized nylon 66 samples tested for comparison.

p-Toluencsulionio acid has the important effect as above noted of repressing to an acceptable level the coloration of the polymer which results from the prcsence of copper. Colorless reducing agents, we have found still further repress the coloration. These include previously proposed additives for nylon such as potassium iodide, phosphorous acid. hypophosphorous acid compounds. etc.

Besides the above noted functions. p-toiucnc-sulionic acid also has the function of limiting viscosity attainable in the polymerization, when used in amounts of about 0.1% by weight and greater. Thus, in polymerizations conducted as in Example I above using 0.6% p-tolucncsulfonic acid a steady polymer viscosity of about 1.60 (reduced viscosity at 0.52% concentration in metacrcsol at 25 C.) was reached after about 18 hours at 255' C.; and using 0.9% p tolucncsulfonic acid a steady mcta-crcsol reduced viscosity of the polymer of about 1.10 was reached after about 9 hcnus at 255 0. Accordingly it should be understood that when p-toluencsulionic acid is present in molten polyceproemide it probably undergoes a reaction with end groups of the polymer. In the claims bcl'nv. the p-toluenesulfonic acid thus present is described as "incorporated" in the polycaproemide.

in Table IV below. examples using various arylsuli'onic acids or normal salts thereof instead of p-toiuenesuifonic acid are presented.

Table IV Additives Percent Loss in Ultimate Tensile Strength Thermal Weath- Color ol yarn Stability crom- Outdoor Exposure (Days) Sulionlc Cmpd. and Gone. CuCh.2l'l|O Cone. ctcr and p.p.m.

30 hrs. 100 hrs. 92 hrs. 30 60 90 120 BL X OHSOI 0.11114 43 print... oil-whim 9 s1 10 XI.. (BIO-80min 0.0114 70, 43 p.p.m. White 2 21 1o r 10 7 D E1. AIL... NI! 50111 0.012%, p.p.m.... Light Lavender... ll 22 i 10 n 12 u NIT,

I0 "I 9 r11. xm n soar 0.012%, 15 p.p.m.... Light Tan e 21 e H 12 la T113080; XIV ib-Q .012%. 15 p.n.m...- ....-do 10 7 :g a? t:

OaNB

M '10 '1 -11 Ex. xv mosoow 0.012% p-n-m----- a Yellow 4 7 1a 12 11 CH: Ex. XVI... "SOQ 0.012%, is p.p.rn...- Oil-White o o Er. XVIL. 80111 0111147,, 43 ppm... Oil-White Ornytah 0 8 Green Tint.

I Concentration in wei rbt ercent based on caprolaetnrn Top tlgure ll Ecrcont on n I Aniline Lb-d ulionlo acid Na salt.

I l-naphthylamine-tJ-dlaulfonic acid.

ultimate tensile atrcnzth ol the atablllted nylon ea yarn control (210 denier, 34 filament count).

We have found that certain other arylsulfonic acids, 00 incorporated therein, was equal or superior in light and but not all arylsullonic acids, function generally similarly to p-toluenesulfonic acid. Those acids which are cfiective are free of chromophoric groups, such as carbony], phenylvinylene, etc. attached to the cry] nucleus. The examples and tests tabulated above in Table IV were carried out essentially as for Example II and Tables 1-1 above, but substituting for p-toluene-aulfonic acid of Example ll, the eult'onlc acids shown in Table IV, in the weight percent: shown. Examples XII-XV incluelve were run simultaneously in the outdor exposure teats, together with a almilar 210 denier-34 filament agingetabilleed nylon 66 yarn for comparison. it will be noted that none of these yarns equalled the nylon 66 yarn in weathering stability, whereas the similar yarn of Example IV in Table II, having p-toluenesultonlc acid 75 tension is also possible;

weathering stability to the like nylon 66 yarn tested for comparison. The yarn of Example XVI having 2,5-dimethyl-benzenesulfonic acid incorporated therein ap pears to have excellent light and weathering stability and has nearly 'white color. Contormably to the foregoing, preferred ary lsulfonic compounds for use in our compositions are the methyleubstituted arylsulfonic compounds, especially the methyl-substituted benzenesulfonic acids and above all, p-toluenesulfonic acid.

In the above examples the copper compound and ptolueneaulfonlc acid were added in the polymerization charge. However, these additives can be added later in the polymerization cycle. Addition thereof to the tinished molten polymer followed by homogenization by exas is blending of the additives 1 1 with solid polycaproamide pellets in a suitable blending apparatus, followed by melt extrusion and repelletlng.

Copper compounds soluble in polyamides which can be employed are ouprous and cupric compounds, e.g. copper salts of organic or inorganic acids, including the copper compounds proposed heretofore for stabilization of polyamides such as those of French Patent 906,893 diivr June 4, 1945 (1.0.) and metallic copper powder (which is observed to react with or dissolve in polynmides); also copper butyrate, citrate, lactate, oleate, oxalate, stearate and tartrate; also copper benzoate and hydroxybenzoic acid salts of copper such as copper salicylate; also the sulfonic acid copper salts including cop per p toluenesulfonate and copper phenolsulfonate; etc.

Instead of the specific antioxidant employed in Examples VIII and IX of Table Ill, others of the aryl organic, nitrogen or phosphorus containing types can be employed and will also improve the thermal stability of yarn produced from the resulting compositions. Examples include other diarylamine-ketone reaction products containing the meso-dialkyl acridan nucleus, both relatively high temperature, high pressure liquid products such as "BLE supplied by Naugatuck Chemical Division and relatively low temperature, low pressure solid reaction products such as "Aminox and "Bctanox Special" supplied by Naugatuck Chemical Division; also substituted diphenyl amines such as alkylatcd diphenylamines e.g. Agerite Stalite" of R. T. Vanderbilt Co., and para-(p-toluene-sulfonylamido) diphenyl amine; also diaryl-p-phenylcne dinmines such as "Wingstny 100" supplied by Goodyear Tire & Rubber Co.; also alkylatcd aryl phosphite, e.g. Naugatucks "Polygard," etc.

These antioxidants are used suitably in amounts between 0.l% and 5% by weight. They appear to operate in presence of the copper compound to produce greater resistance to heat degradation in polycaproamide than is obtaintable with antioxidant alone, pan ticulariy higher resistance to breaking at elevated temperatures and under load than obtained with copper alone or with antioxidant alone. For example a yarn generally as in Example IX of Table III above was tested for thermal stability under load as follows:

840 denier. 136 filament yarn was spun from a polycaproamide composition and drawn essentially as for Example lX above, except that the antioxidant consisted of only the "BXA" diphenylaminc-acetone condensation product after-treated with formaldehyde, used as the major ingredient of the antioxidant of Example lX.

Samples of the yarn were exposed in a single layer on 2 inch aluminum bobbins in an air-circulating oven regulatcd at 16512 C. for 2, 4, 8 and 16 hours. The samples were then conditioned for 2 hours at 65% relative humidity. Under a 2000 gram load, the samples were then subjected to increasing temperatures, increasing at t C. per 48 seconds until the sample broke.

The results are shown in Table V which follows, to-

gether with results on a like yarn containing no copper.

The polymers of caproiactam which can be improved in accordance with this invention are typified by the homopolymers of the above examples, but include homopolymers otherwise produced, e.g. using catalysts and/or viscosity stabilizers such as adipic acid, hexamethylene diaminc, benzylaminet-carboxyiic acid, etc.; and also include copolymers, e.g. with adipic acid-hexamethylcnc diamine salt, or with an amino acid, wherein a substantial proportion of the constituents is polymerized caprolactam.

The polymers and yarns of this invention can be modified by the addition of materials such as delustrants, pig mcnts, fillers, resins, plasticizers, and others conventionly used in polymer compositions.

The yarns of this invention can be dyed, the dyeability being dependent upon the copper compound employed. Cupric phosphate and cupric chloride additivcs afford yarns which dye much more deeply than yarns containing other copper compounds, e.g. cupric acetate.

The compositions of this invention containing a copper salt and "BXA antioxidant with or without other materials, e.g. as in Example 1X hereof and Table V hereof, are especially suited for production of tire yarn and yarn for marine and other outdoor uses. This special utility is due to the unusual combination of high drawability of filaments spun from these compositions giving high tcnacitics, and their excellent aging resistance against both heat and atmospheric influences as above outlined.

We claim:

1. A polycaproamidc stabilized against aging, having copper dissolved therein and in which is incorporated at least 3 molecular proportions per atomic proportion of copper, of at least one sulfonic compound of the group consisting of arylsulfonic acids and derivatives hydrolyzable thereto, free of chromophoric groups.

2. Composition as defined in claim 1 wherein the copper is present in amounts between about 5 and about 500 parts per million by weight based on the polycaproamidc and the sulfonic compound present is paratoluenesulfonic acid in amount between about 0.1% and about 2% by weight based on the polycaproamide.

3. The composition as defined in claim 2 wherein there is additionally present a diarylamine-ketone reaction product containing the meso-dialkyl acridan nucleus.

4. Composition as defined in claim 1 wherein copper is present iri amounts between about 10 and about parts per million by weight based on the polycaproamide and the sulfonic compound present is para-tolucnesulionic acid in amount between about 0.1% and about 1% by weight of the polycaproamide.

5. Composition as defined in claim 4 wherein the copper is incorporated as cupric chloride.

6. Composition as detined in claim 4 wherein there is additionally present a high temperature, high pressure reaction product of diphenyiarnlne and acetone, further reacted with formaldehyde to form therefrom a waterinsoluble solid, fusable condensation product.

7. Composition as defined in claim 6 in the form of a drawn filament.

8. Composition as defined in claim 1 wherein there is additionally present at least one organic anti-oxidant ot the group consisting of diarylamine-kctone reaction products containing the meso-dialkyl acridan nucleus; alkylated diphenylaminea; para-(para-tolucne-sulfonylamldo)- diphenylamine; dluryl-para-phenylene diamines; and al ltylated aryl phosphates.

9. Composition as defined in claim 1 wherein the nulfonic compound it a methyl-substituted benunc-aulfonlc acid.

10. Composition of claim 2 wherein copper compount and para-toluenesulfonlc acid are the sole ingredients of 13 l 19 1949 1h 0m sition im artin thereto stability to outdoor 2,476,661 Hart Iu y wtfatileri g and to hzfat. 3 2,560,033 Webb July 10, 1951 2,705,227 Stamatofi Mar. 29, 1955 References Cited in the file ofthns patent 2,960,489 Gabkr et a]. 15 1960 UNITED STATES PATENTS 5 3,003,995 Schule Oct. 10, 1 1 1,906,942 Horst May 2, 1933 UNITED STATES PATENT OFFICE Patent N0. 3, 113, 120 December 3, 1963 Patrick V. Paper-o, Jr. et a1 It is hereby certified that error appears in the above numbered patent requiring correction and that the said Letters Patent should read as corrected below.

Columns 3 and 4 Table I in the title to the table after "PERCENT" insert LOSS column 4, line 33, for "ever" read every column 9, line 70, for "outdor" read outdoor column l2 lines 13 and 14, for "convention 1y" read conventionally line 69 for "phosphates read phosphites Signed and sealed this 28th day of April 1964.

(SEAL) Atteat:

ERNEST W. SWIDER EDWARD J.. BRENNER Attesting Officer Commissioner of Patents 13 l 19 1949 1h 0m sition im artin thereto stability to outdoor 2,476,661 Hart Iu y wtfatileri g and to hzfat. 3 2,560,033 Webb July 10, 1951 2,705,227 Stamatofi Mar. 29, 1955 References Cited in the file ofthns patent 2,960,489 Gabkr et a]. 15 1960 UNITED STATES PATENTS 5 3,003,995 Schule Oct. 10, 1 1 1,906,942 Horst May 2, 1933 UNITED STATES PATENT OFFICE Patent N0. 3, 113, 120 December 3, 1963 Patrick V. Paper-o, Jr. et a1 It is hereby certified that error appears in the above numbered patent requiring correction and that the said Letters Patent should read as corrected below.

Columns 3 and 4 Table I in the title to the table after "PERCENT" insert LOSS column 4, line 33, for "ever" read every column 9, line 70, for "outdor" read outdoor column l2 lines 13 and 14, for "convention 1y" read conventionally line 69 for "phosphates read phosphites Signed and sealed this 28th day of April 1964.

(SEAL) Atteat:

ERNEST W. SWIDER EDWARD J.. BRENNER Attesting Officer Commissioner of Patents UNITED STATES PATENT OFFICE CERTIFICATE OF CORRECTION Pa tent No, 3, 113, 120 December 3, 1963 Patrick V. Pepero, Jr., et a1.

Columns 3 and 4, Table I in the ti tle to the table, af ter "PERCENT" insert LOSS column 4 line 33, for "ever" read every column 9 line 70, for "outdor" read outdoor column 12, lines 13 and 14, for "convention 1y" read conventionally line 69 for "phosphates read phosphites Signed and sealed this 28th day of April 1964.

(SEAL) Alteat:

ERNEST W. SWIDER EDWARD J. BRENNER Atteating Officer Commissioner of Patents 

1. A POLYCAPROAMIDE STABILIZED AGAINST AGING, HAVING COPPER DISSOLVED THEREIN AND IN WHICH IS INCORPORATED AT LEAST 3 MOLECULAR PROPORTIONS PER ATOMIC PROPORTION COPPER, OF AT LEAST ONE SULFONIC COMPOUND OF THE GROUP CONSISTING OF ARYLSULFONIC ACIDS AND DERIVATIVES HYDROLYZABLE THERETO, FREE OF CHROMOPHORIC GROUPS.
 4. COMPOSITION AS DEFINED IN CLAIM 1 WHEREIN COPPER IS PRESENT IN AMOUNTS BETWEEN ABOUT 10 AND ABOUT 100 PARTS PER MILLION BY WEIGHT BASED ON THE POLYCAPROAMIDE AND THE SULFONIC COMPOUND PRESENT IS PARA-TOLUENESULFONIC ACID IN AMOUNT BETWEEN ABOUT 0.1% AND ABOUT 1% BY WEIGHT OF THE POLYCAPROAMIDE.
 6. COMPOSITIONAS DEFINED IN CLAIM 4 WHEREIN THERE IS ADDITIONALLY PRESENT A HIGH TEMPERATURE, HIGH PRESSURE REACTION PRODUCT OF DIPHENYLAMINE AND ACETON, FURTHER REACTED WITH FORMALDEHYDE TO FORM THEREFROM A WATERINSOLUBLE SOLID, FUSABLE CONDENSATION PRODUCT. 